Tape backup has been used since before hard disk backup and the technology is both stable and reliable though not as quick as a direct backup. Two of the main tape backup solutions fro linux are Amanda and Bacula. These are described in a nutshell as follows:

Amanda is a backup system that allows the administrator of a LAN to set up a single master backup server to back up multiple hosts to a single large capacity tape drive. AMANDA uses native dump and/or GNU tar facilities and can back up a large number of workstations running multiple versions of Unix.

Bacula is a set of computer programs that permit you (or the system administrator) to manage backup, recovery, and verification of computer data across a network of computers of different kinds.

Either solution will work to backup and restore your data. In the end which solution you go for depends very much on your particular requirements.

IP Address in Decimal And Binary Notation

The above IP address is expressed in decimal or "dotted" form. A computer will actually use the binary form of the address which for this address is:
01001000.00010101.11001110.00000101
The four numbers that you see in an IP address are called octets. This is because they each have eight numbers or positions when expressed in binary form.

In total an IP address in binary form has 32 numbers each of which can take the value 0 or 1.

For each octet the total number of different combinations is 2 to the power of 8 or 255 values. So each octet can contain the values 0 up to 255.

For example the address 255.255.255.255 is used for network broadcasts.

In order to become an expert in reading IP addresses you really need to understand binary to decimal conversion. This will be covered in a later post. In the meantime knowing the different types of Ip address class will certainly help.

IP Address Classes

There are different classes of IP address. The IP address is seen as having two parts - a part used to identify the network and a part used to identify the host or computer on that network. In the examples below the n stands for network bit and the h stands for host bit.

Class A - 0nnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh ,
first bit is 0, 7 network bits, 24 host bits. In this case there can be 126 networks and each network can contain up approx 17 million hosts. So you can see that this class is used for large networks.

Class B - 10nnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh ,
first two bits 10, 14 network bits, 16 host bits. Each B class can have 65,532 hosts. In this case there can be 16,384 networks and approx 65,000 hosts per network. This class is used for medium sized networks.

Class C - 110nnnnn nnnnnnnn nnnnnnnn hhhhhhhh , first three bits 110, 21 network bits, 8 host bits. This is typically used for LANs (local area networks). Each C class can have 254 hosts

Class D - 1110mmmm.mmmmmmmm.mmmmmmmm.mmmmmmmm , first four bits 1110, 28 multicast bits. These are multicast addresses.

Class E - 1111rrrr.eeeeeeee.eeeeeeee.eeeeeeee , first four bits 1111, 28 reserved bits. This class is reserved for experimental use.

I hope that this article has helped you, at least to some extent, learn how to read  ip addresses.

]]> http://www.infrastructuredesigntoday.com/how-do-you-read-an-ip-address/feed/ http://www.infrastructuredesigntoday.com/why-do-you-need-a-web-server/ http://www.infrastructuredesigntoday.com/why-do-you-need-a-web-server/#comments Tue, 08 Jul 2008 21:56:37 +0000 tony1kenobi http://www.infrastructuredesigntoday.com/why-do-you-need-a-web-server/ This is a basic overview of why you might need a web server. All websites use web servers. The name comes from the fact that the the server actually servers web pages just like this one! So lets take this page as an example of a page served by a web server.

In order to reach this page you searched for the term "why do you need a web server" in Google or Yahoo or MSN. When you clicked the google page result with the name of this page a request went to a server in this websites datacenter. The web server (in this case Apache) is listening for these requests - yours included. When it receives a request it looks to see if the page that you requested is available and of course it is as you are looking at it :-). So it sends the page back to your browser.

So from this websites perspective we need a web server in order to be able to respond to requests for web pages. The web server is the point of entry to the website and any backend systems that it might interface with. A database is a good example of a backend system. This site uses Worpress which in turn uses a MYSQL database. So when our web server received your page request it first retrieved the page information from the database and then displayed it to you.

In a nutshell the web server is the software that "serves" the website pages to your browser.

1. scalablity
2. high availability
3. performance

All other factors such as fault tolerence, resilience etc can be captured under the above three factors. And technologogies such as server load balancing and clustering can fit under the high availability factor.

A typical SAN configuration contains a combination of disk arrays, special SAN switches and special software. A SAN is a dedicated network of data storage devices that is intended to provide high availabability, high performance and data redundancy. It achieves this through combining a number of hardware technologies and assocaited software.

SINA - the Storage Network Industry Association defines a SAN as:
"a network whose primary purpose is the transfer of data between computer systems and storage elements"

I would extend this definition to include the data stroage elements such as the disk arrays as they really are part of the overall SAN solution.

Information Infrastructure Design is the design of infrastructure for information systems such as websites. A good way to look at information infrastructure design is to look at what the components of a typical infrastructure are. So in no particular order lets list some of them:

• a storage area network or SAN
• network attached storage or NAS
• network hubs, routers and switches
• application servers
• web servers
• backup servers
• tape backup devices

So in designing an infrastructure we are really taking all of the above components and orchestrating them so that we can provides the services that we want to provide.